The present invention relates generally to fluid delivery devices and, more specifically, to a fluid delivery device providing a pulsating discharge and to a cleaning method using such a device.
In various cleaning operations, such as the cleaning of circuit boards, a fluid, which may be a solvent for the contamination to be removed, is discharged and sprayed upon the area to be cleaned to contact the contamination. Often, such fluid is discharged in a steady stream that impacts the surface with a constant force. In many cases, the steady pressure of such a constant fluid stream and the solvent properties of the fluid are adequate to remove the contamination. The cleaning fluid is recycled in many applications.
As the use of chemical-based and petroleum-based solvents has become environmentally undesirable, cost-prohibitive, or both, more cleaning applications are being performed with water or aqueous cleaning fluids. Water or aqueous cleaning fluids often require added mechanical action, however, to provide the same cleaning ability as provided by chemical-based or petroleum-based solvents. Water conservation is also desirable not only to restrict water consumption, but also to limit waste treatment costs.
For any of the above reasons, it may be preferable to provide a pulsating stream of cleaning fluid aimed at the surface to be cleaned. Furthermore, in some applications the object to be cleaned, such as a circuit board, has a certain width and is moved past the cleaning device. In such applications it may be useful to provide the pulsating stream in the form of a sheet or curtain of discharged fluid. Although there are many ways known in the art for providing pulsating action in general, the present invention proposes a design that is particularly useful for providing a pulsating spray of liquid for cleaning circuit boards.
The deficiencies of the conventional fluid delivery devices show that a need still exists for an improved fluid delivery device and for a cleaning method using an improved device. To overcome the shortcomings of the conventional devices and methods, a new fluid delivery device and cleaning method are provided. An object of the present invention is to meet the requirements of those cleaning applications limited to in water or aqueous cleaning fluids. A related object is to provide a device and method having a cleaning ability comparable to that achieved by devices and methods using chemical-based or petroleum-based solvents. Another object is to provide a device and method offering water conservation. Still another object of the present invention is to provide a device and method that use a pulsating spray of liquid for cleaning circuit boards.
To achieve these and other objects, and in view of its purposes, the present invention provides a fluid delivery apparatus for supplying a linear pulsating discharge of a first fluid from a source of the first fluid. The apparatus comprises a housing, an elongated cylindrical chamber within the housing, an elongated cylindrical rotor rotatably mounted in the chamber and having a plurality of grooves, and a linear fluid discharge in the housing connected to the chamber. A first fluid injector passage in the housing is connected to the source of the first fluid and the chamber, and comprises a first fluid injection channel. The channel is shaped to accelerate the first fluid and to direct the accelerated fluid into the grooves of the rotor, causing the rotor to rotate. The rotor has an outside diameter sized to substantially wipe the inside diameter of the chamber. The linear fluid discharge may comprise a plurality of individual, linearly aligned orifices.
The grooves in the rotor may be helical and aligned with one linear portion of the linear fluid discharge in one position of the rotor and aligned with another linear portion of the linear fluid discharge in another position of the rotor. The helical grooves are adapted to provide a pulse of fluid that traverses the linear fluid discharge from one linear portion to the other upon rotation of the rotor from one position to the other. The rotor may comprise a first helical groove disposed in a clockwise helix and aligned with a first section of the linear fluid discharge and a second helical groove disposed in a counter-clockwise helix aligned with a second section of the linear fluid discharge.
The apparatus may comprise a second fluid injection channel in the housing connected to a source of a second fluid. The second fluid injection channel is adapted to inject the second fluid into the rotor grooves to be ejected through the linear fluid discharge. One of the first and second fluids may be a compressible fluid, such as air, and the other an incompressible fluid, such as water.
The invention also comprises a method for cleaning an object using the above apparatus. The method comprises (a) passing the first fluid into the first fluid injector passage and into the first fluid injection passage; (b) impinging the first fluid upon the grooves in the rotor, thereby rotating the rotor; and (c) ejecting a pulse of the first fluid through the linear fluid discharge onto the object, such as a circuit board. When the apparatus further comprises the second fluid injection channel, the method further comprises, between steps (b) and (c), injecting the second fluid into the second fluid injection channel and impinging the second fluid into the grooves in the rotor and, in step (c), ejecting the second fluid from the linear fluid discharge along with the first fluid.
When the grooves in the rotor are helical as described above, the method further comprises, in step (c), ejecting the fluid so that the pulse traverses the fluid discharge from one linear portion to the other linear portion as the rotor rotates from the one position to the other. When the linear fluid discharge comprises a plurality of individual orifices aligned linearly from a first orifice to a second orifice with a set of orifices in between, the method further comprises ejecting the first fluid in a pulse that sequences linearly from the first orifice through the set of orifices to the second orifice. The pulse may start at the center of the linear fluid discharge and end at the opposite ends, start at the opposite ends and end at the center, or travel from end to end.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.